I caught a movie on SyF, back when it was still called The Sci-Fi Channel, ages ago. Hell, I think it might have been when the channel was still pretty young. Anyway, caught a flick back then and forgot the name of it. It was about a couple guys and a woman searching for treasure in a mine shaft or cave. Of course, it turns out not to be an easy task; the shaft was infested by some killer primordial ooze. Things I remember about the movie:

-Black and white-One of the guys winds up falling in the ooze and dying-I don't think there was a very high death toll-I seem to remember one scene where one of the characters is in a bar and a mariachi begins singing about the cave and possibly the lifeform living in it-I remember scenes of the ooze coming out of the walls and running down it in cascades

If it was B&W, I am almost sure this has to be "The Unknown Terror" (1957).

I agree with Andrew-it even mentions the calypso singer and the song in this review from imdb-

I remember seeing this as a kid on local TV and being somewhat put out by the fact that you never got a clear look at the infected natives (probably for good reasons) and that the killer fungus monster at the finale was obviously tons of soap suds mixed in with a little dry ice fog. Oddly enough it stuck with me and soon I was putting shampoo in my hair and screaming "The fungus,the fungus!" Still,the leads all do a good straight faced job and the script doesn't contain the amount of Ed Wood style howlers you'd expect it to.As far as I know this is also the last horror film to present calypso singer Sir Lancelot who had appeared in the Val Lewton Films I walked with a Zombie and Curse Of The Cat People. The song "You Got To Suffer To Be Born Again is a mix of genius and absurdity. Highly recommended to anyone who likes old B movies.

Hmm... That almost sounds right, but I don't remember there being any fungal monsters. After watching a clip on YouTube, the film also doesn't seem like the right one. I might have to watch the whole movie, but I do remember the antagonist being a kind of slime or ooze.